Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)

"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Mon, 20 November 2017 21:40 UTC

Return-Path: <ginsberg@cisco.com>
X-Original-To: isis-wg@ietfa.amsl.com
Delivered-To: isis-wg@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 28078128CD5; Mon, 20 Nov 2017 13:40:20 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -14.519
X-Spam-Level:
X-Spam-Status: No, score=-14.519 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_PASS=-0.001, URIBL_BLOCKED=0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cisco.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VE-doB9m7qBo; Mon, 20 Nov 2017 13:40:18 -0800 (PST)
Received: from rcdn-iport-9.cisco.com (rcdn-iport-9.cisco.com [173.37.86.80]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 2BBD1126FDC; Mon, 20 Nov 2017 13:40:18 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=12594; q=dns/txt; s=iport; t=1511214018; x=1512423618; h=from:to:cc:subject:date:message-id:references: in-reply-to:mime-version; bh=MaxXMD8Jw/UwiWsjyDZo33z83NdCsa96f5xbzzfeJec=; b=FWZammtzFBeawWNrCKyZP8CB7Gt45e8Z3vpyYtwIucaOPdUSuGKv7C8j cbFRGwRVQ6byi7B4E//QjueIwtXfzkLp8KSAM0xPAYbhJ7vk6g3x8bivR MYo+q9MTf5L+7Ns24b9QdJAw/p9qP8YdULDAPLAtpx3a/rOqHpmcD1/83 A=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: =?us-ascii?q?A0D8AAChShNa/4YNJK1bGQEBAQEBAQEBA?= =?us-ascii?q?QEBAQcBAQEBAYJKcmZuJweDeIofjyiBfZEZhUmCEQoYAQqFGAIahGM/GAEBAQE?= =?us-ascii?q?BAQEBAWsohR4BAQEBAwEBIQpBCxACAQgRBAEBKAMCAgIlCxQJCAIEAQ0FCIk5Z?= =?us-ascii?q?BCoSIIninYBAQEBAQEBAQEBAQEBAQEBAQEBAQEYBYM0ggeBVYUUhVGCX4JjBaI?= =?us-ascii?q?+ApUBk1WWBQIRGQGBOQEfOYF0ehVJgmSEX3eKPoEUAQEB?=
X-IronPort-AV: E=Sophos;i="5.44,429,1505779200"; d="scan'208,217";a="316824141"
Received: from alln-core-12.cisco.com ([173.36.13.134]) by rcdn-iport-9.cisco.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 20 Nov 2017 21:40:17 +0000
Received: from XCH-RCD-014.cisco.com (xch-rcd-014.cisco.com [173.37.102.24]) by alln-core-12.cisco.com (8.14.5/8.14.5) with ESMTP id vAKLeHUo007478 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Mon, 20 Nov 2017 21:40:17 GMT
Received: from xch-aln-001.cisco.com (173.36.7.11) by XCH-RCD-014.cisco.com (173.37.102.24) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Mon, 20 Nov 2017 15:40:16 -0600
Received: from xch-aln-001.cisco.com ([173.36.7.11]) by XCH-ALN-001.cisco.com ([173.36.7.11]) with mapi id 15.00.1320.000; Mon, 20 Nov 2017 15:40:16 -0600
From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: Tony Przygienda <tonysietf@gmail.com>, "Acee Lindem (acee)" <acee@cisco.com>
CC: "isis-wg@ietf.org" <isis-wg@ietf.org>, "draft-hegdeppsenak-isis-sr-flex-algo@ietf.org" <draft-hegdeppsenak-isis-sr-flex-algo@ietf.org>
Thread-Topic: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)
Thread-Index: AQHTYiwUorBcn9y+VUye45yg4W6jQ6MeKGSA//+iMUA=
Date: Mon, 20 Nov 2017 21:40:16 +0000
Message-ID: <10c5fdd91d1c404db7ca00bcb7e31730@XCH-ALN-001.cisco.com>
References: <D63886A4.DA829%acee@cisco.com> <CA+wi2hPsF1NJTLH_D1X5jpCGBhc0U9yoKU1cG3UNnwQbiUwWxw@mail.gmail.com>
In-Reply-To: <CA+wi2hPsF1NJTLH_D1X5jpCGBhc0U9yoKU1cG3UNnwQbiUwWxw@mail.gmail.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: [10.24.94.50]
Content-Type: multipart/alternative; boundary="_000_10c5fdd91d1c404db7ca00bcb7e31730XCHALN001ciscocom_"
MIME-Version: 1.0
Archived-At: <https://mailarchive.ietf.org/arch/msg/isis-wg/um2XWJ3V8pVolvIwnfSjpJUM6I0>
Subject: Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)
X-BeenThere: isis-wg@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: IETF IS-IS working group <isis-wg.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/isis-wg>, <mailto:isis-wg-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/isis-wg/>
List-Post: <mailto:isis-wg@ietf.org>
List-Help: <mailto:isis-wg-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/isis-wg>, <mailto:isis-wg-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 20 Nov 2017 21:40:20 -0000

Tony –

My understanding is that algorithm definitions are topology independent. This is consistent with the two algorithms defined today (standard SPF and strict-spf).
Using an algorithm in a particular topology would require topology/algorithm specific SIDs and the advertisement of topology specific link attributes (i.e., in an MT specific IS Neighbor).

   Les


From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of Tony Przygienda
Sent: Monday, November 20, 2017 1:11 PM
To: Acee Lindem (acee) <acee@cisco.com>
Cc: isis-wg@ietf.org; draft-hegdeppsenak-isis-sr-flex-algo@ietf.org
Subject: Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)

So, it seems that there will be a new draft with 242 covering all algorithms (i.e. no MT specific algo advertisement anymore).

Then I thought each MT advertises which Flex it supports. Is the assumption that you can run multiple algorithms per MT? How would you otherwise have a two-algorithms-to-same-prefix problem?

Is there some kind of conceptual model of FlexAlgo, i.e. how many of what associated with how  many of the other (MT to algo, algo to protocol instance etc) ...

-- tony

On Mon, Nov 20, 2017 at 10:19 AM, Acee Lindem (acee) <acee@cisco.com<mailto:acee@cisco.com>> wrote:
Hi Shraddha, Peter, et al,

The comment on the draft I had was that the conflict case where two ISIS routers advertise the same multi-homed prefix with a different algorithm needs to be covered. I wouldn’t try and optimize for this and would just do whatever is simplest but avoids loops (e.g., log the situation and prefer the path computed with the lowest numbered algorithm).

Thanks,
Acee

_______________________________________________
Isis-wg mailing list
Isis-wg@ietf.org<mailto:Isis-wg@ietf.org>
https://www.ietf.org/mailman/listinfo/isis-wg